3*atan(3*x)
9 -------- 2 1 + 9*x
-162*x ----------- 2 / 2\ \1 + 9*x /
/ 2 \ | 36*x | 162*|-1 + --------| | 2| \ 1 + 9*x / ------------------- 2 / 2\ \1 + 9*x /